1. Field of the Invention
The present invention relates to an air conditioning plant and a control method thereof, and more particularly to an air conditioning plant capable of optimal operation optimized with a view to energy conservation, operating cost reduction and conservation of the global environment and a control method thereof.
2. Description of the Related Art
Japanese Patent Application Publication No. 2002-98358 discloses a primary pump type heat source current transformation system which air-conditions a building by supplying in a circulatory manner cold or hot water from only a heat source side. This system comprises a cold/hot water generator which supplies cold or hot water to an air conditioner, a cooling tower which supplies cooling water to the cold/hot water generator, and a pumping variable flow rate control unit which performs variable control so as to supplying in a circulatory manner the cold or hot water and the cooling water according to the air conditioning load, and the power consumption by a cooling water pump and a cold water pump is reduced by varying the flow rates of the cold or hot water and the cooling water.
However, as the air conditioning method disclosed in Japanese Patent Application Publication No. 2002-98358 is to reduce the power consumption by the cooling water pump and the cold water pump by varying only the flow rates of the cold or hot water and the cooling water, the control is not designed to reduce the overall power consumption by the air conditioning plant, and accordingly it is not possible to reduce power consumption by the whole air conditioning plant.
An object of the present invention, attempted in view of the circumstances noted above, is to provide an air conditioning plant capable of reducing the whole energy consumption, the operating cost or the carbon dioxide emission of the whole air conditioning plant and a control method thereof.
In order to attain the object stated above, the present invention is directed to a control method of an air conditioning plant having at least one air conditioner, a low/high-temperature heat generator which supplies a low/high-temperature heat transfer medium to the air conditioner, and a heat source/sink which supplies a heat discharging/absorbing medium to the low/high-temperature heat generator, whereby the setpoints of at least the draft temperature of the at least one air conditioner, the low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and the heat discharging/absorbing medium temperature of the heat source/sink are optimized so as to reduce at least one of the energy consumption, the operating cost and the carbon dioxide emission of the air conditioning plant within the extent of satisfying the set conditions of air conditioning.
The present invention is also directed to an air conditioning plant having at least one air conditioner, a low/high-temperature heat generator which supplies a low/high-temperature heat transfer medium to the air conditioner, and a heat source/sink which supplies a heat discharging/absorbing medium to the low/high-temperature heat generator, wherein the setpoints of at least the draft temperature of the at least one air conditioner, the low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and the temperature of the heat discharging/absorbing medium from the heat source/sink can be optimized so as to reduce the energy consumption, the operating cost or the carbon dioxide emission of the air conditioning plant within the extent of satisfying the set conditions of air conditioning.
The present invention is also directed to a control method of an air conditioning plant comprising at least one air conditioner, at least one low/high-temperature heat generators which supply a low/high-temperature heat transfer medium to the air conditioner, a heat source/sink which cools or heats the low/high-temperature heat generator, a low/high-temperature heat accumulator which stores the low/high-temperature heat transfer medium during a period of a low low/high-temperature heat load, heat transfer medium conveying units, such as pumps, fans and blowers, which connect the aforementioned devices, and control units which control the temperatures of heat generated by these devices and/or the flow rate of conveying the heat transfer medium, further provided with a group of measuring instruments with which data representing the operating states of individual units including the temperature and the flow rate are measured, a group of control units with which the operation of individual units is controlled, and a central monitoring device which is linked by signal lines to the group of measuring instruments and the group of control units, wherein the central monitoring device has, built into it, at least either an air conditioning plant operation simulator which manages the operation of the whole air conditioning plant or an air conditioning plant operational data table; computes on the basis of real time operational data picked up by the measuring instruments the optimal operating temperature and the optimal flow rate for the constituent units of the air conditioning plant and the optimal number of operating units of at least one of the low/high-temperature heat generators to minimize the energy consumption, operating cost or carbon dioxide emission equivalent or any indicator combining two or more of these factors of the whole air conditioning plant in predetermined ranges of conditions, including the temperature and humidity, of air conditioning, ranges of energy consumption conditions with respect to electric power, fuel, water and so forth, or various permissible areas of condition setting which satisfy the ranges of requirements set by combining these two sets of conditions in a prioritized manner; and supplies those optimal values to the group of control units as control setpoints, and the control unit group generates control signals on the basis of the control setpoints, supplies the control signals to the constituent units of the air conditioning plant or to the pertinent control units themselves to control at least two of the constituent units of the air conditioning plant at substantially the same time.
The present invention is also directed to a control method of an air conditioning plant comprising at least one air conditioner, at least one low/high-temperature heat generators which supply a low/high-temperature heat transfer medium to the air conditioner, a heat source/sink which cools or heats the low/high-temperature heat generator, heat transfer medium conveying units, such as pumps, fans and blowers, which connect the aforementioned devices, and control units which control the temperatures of heat generated by these devices and/or the flow rate of conveying the heat transfer medium, a group of measuring instruments with which data representing the operating states of individual units including the temperature and the flow rate are measured, a group of control units with which the operation of individual units is controlled, and a central monitoring device which is linked by signal lines to the group of measuring instruments and the group of control units, wherein the central monitoring device has, built into it, at least either an air conditioning plant operation simulator which manages the operation of the whole air conditioning plant or an air conditioning plant operational data table; computes on the basis of real time operational data picked up by the measuring instruments the optimal operating temperature and the optimal flow rate for the constituent units of the air conditioning plant and the optimal number of operating units of at least one of the low/high-temperature heat generators to minimize the energy consumption, operating cost or carbon dioxide emission equivalent or any indicator combining two or more of these factors of the whole air conditioning plant in predetermined ranges of conditions, including the temperature and humidity, of air conditioning, ranges of energy consumption conditions with respect to electric power, fuel, water and so forth, or various permissible areas of condition setting which satisfy the ranges of requirements set by combining these two sets of conditions in a prioritized manner; and supplies those optimal values to the group of control units as control setpoints, and the control unit group generates control signals on the basis of the control setpoints, and supplies the control signals to the constituent units of the air conditioning plant or to the pertinent control units themselves to control at least two of the constituent units of the air conditioning plant at substantially the same time.
The present invention is also directed to an air conditioning plant which performs air conditioning by supplying a low/high-temperature heat transfer medium in a circulatory manner, provided with simulation models of low/high-temperature heat generators, pumps and other units constituting the air conditioning plant, wherein optimal control targets to minimize or maximize a performance criterion are determined by simulation, and the air conditioning plant is operated according to the optimal control targets.
The present invention is also directed to an air conditioning plant which performs air conditioning by supplying a low/high-temperature heat transfer medium in a circulatory manner, provided with an equipment characteristics database which stores characteristics data on constituent units of the air conditioning plant, an air conditioning plant simulator which computes power consumptions and fuel consumptions in partial loads from the equipment characteristics data of constituent units stored in the equipment characteristics database, and computes performance functions by using conversion coefficients, and an optimizing device which computes the optimal control targets for the constituent units of the air conditioning plant by using the air conditioning plant simulator, wherein the constituent units of the air conditioning plant are operated according to the optimal control targets.
According to the present invention, so that an air conditioning plant can be operated in the most desirable state, the setpoints of the draft temperature of least one air conditioner, the low/high-temperature heat transfer medium temperature of a low/high-temperature heat generator and the temperature of the heat discharging/absorbing medium from a heat source/sink can be optimized. Thus, the inventors of the present invention discovered, as a result of analyzing these three parameters, that the air conditioning plant could be operated in a highly desirable state. This makes possible simple and prompt accomplishment of efficient operation of the air conditioning plant.
According to the present invention, it is preferable to optimize at least one of the setpoints of the draft air flow rate of the air conditioner, the low/high-temperature heat transfer medium flow rate of the low/high-temperature heat generator and the flow rate of the heat discharging/absorbing medium from the heat source/sink in addition to the draft temperature of the at least one air conditioner, the low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and the temperature of the heat discharging/absorbing medium from the heat source/sink. By adding more parameters to the aforementioned controls, it is made possible to control the operation of the air conditioning plant with greater accuracy.
Further according to the present invention, it is preferable to prepare in advance a data table showing a plurality of combinations of the draft temperature of the at least one air conditioner, the low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and the temperature of the heat discharging/absorbing medium from the heat source/sink and the energy consumption, the operating cost or the carbon dioxide emission of the air conditioning plant at the time, and to alter setpoints by accessing this data table. If a data table is prepared in advance in this manner, prompt control the operation of the air conditioning plant is made possible.
Further according to the present invention, it is preferable that the piping conditions of the at least one air conditioner, the piping conditions of the low/high-temperature heat generator and the piping conditions of the heat source/sink can be entered. If the piping conditions of these units can be entered in this way, application to various air conditioning plants or when the air conditioning plant has been remodeled would be facilitated, resulted in an expanded range of applicability of the air conditioning plant and the control method therefor pertaining to the present invention. Incidentally, the piping conditions include the number of piping lines, the piping length, pipe bore, pressure loss and other factors of each unit.
Further according to the present invention, efficient operation of the air conditioning plant can also be accomplished simply and promptly in the air conditioning plant provided with a low/high-temperature heat accumulator which stores the low/high-temperature heat transfer medium in a period of a lighter low/high-temperature heat load in addition to the air conditioner, the low/high-temperature heat generator and the heat source/sink.
The present invention is also directed to an air conditioning plant comprising an air conditioner, a low/high-temperature heat generator and a heat source/sink further provided with a group of measuring instruments with which data representing the operating states of individual units including the temperature and the flow rate are measured, a group of control units with which the operation of individual units is controlled, and a central monitoring device which is linked by signal lines to the group of measuring instruments and the group of control units, wherein the central monitoring device has, built into it, at least either an air conditioning plant operation simulator which manages the operation of the whole air conditioning plant or an air conditioning plant operational data table; computes on the basis of real time operational data picked up by the measuring instruments the optimal operating temperature and the optimal flow rate for the constituent units of the air conditioning plant and the optimal number of operating units of at least one of the low/high-temperature heat generators to minimize the energy consumption, operating cost or carbon dioxide emission equivalent or any indicator combining two or more of these factors of the whole air conditioning plant in predetermined ranges of conditions, including the temperature and humidity, of air conditioning, ranges of energy consumption conditions with respect to electric power, fuel, water and so forth, or various permissible areas of condition setting which satisfy the ranges of requirements set by combining these two sets of conditions in a prioritized manner; and supplies those optimal values to the group of control units as control setpoints, and the control unit group generates control signals on the basis of the control setpoints, and supplies the control signals to the constituent units of the air conditioning plant or to the pertinent control units themselves to control at least two of the constituent units of the air conditioning plant at substantially the same time. Efficient operation of the air conditioning plant is thereby made possible simply and promptly.
Further according to the present invention, it is preferable that the central monitoring device has a unit which enters from outside the priority ranks or the minimization indicators, on the basis of and the various permissible areas of condition setting performs the minimizing computations, generates optimal control values and controls at least two of the constituent units of the air conditioning plant at substantially the same time, with the result that efficient operation of the air conditioning plant is thereby made possible simply and promptly.
Further according to the present invention, it is preferable that at least one of the units having devices which externally supply and display the energy consumption, the operating cost and the instantaneous value and the integrated value of the carbon dioxide emission equivalent of the whole air conditioning plant is provided with the central monitoring device.
The present invention is also directed to an air conditioning plant which performs air conditioning by supplying a low/high-temperature heat transfer medium in a circulatory manner comprising simulation models of low/high-temperature heat generators, pumps and other units constituting the air conditioning plant, wherein optimal control targets to minimize or maximize a performance criterion are determined by simulation, and the air conditioning plant is operated according to the optimal control targets. This makes possible prompt control of the operation of the air conditioning plant. Also, the performance criterion here is supposed to be the energy consumption, but it can as well be the operating coast or the carbon dioxide emission equivalent.
The present invention is also directed to an air conditioning plant which performs air conditioning by supplying a low/high-temperature heat transfer medium in a circulatory manner, comprising: an equipment characteristics database which stores characteristics data on constituent units of the air conditioning plant; an air conditioning plant simulator which computes power consumptions and fuel consumptions in partial loads from the equipment characteristics data of constituent units stored in the equipment characteristics database, and computes performance functions by using conversion coefficients; and an optimizing device which computes the optimal control targets for the constituent units of the air conditioning plant by using the air conditioning plant simulator, wherein the constituent units of the air conditioning plant are operated according to the optimal control targets. This makes possible prompt control of the operation of the air conditioning plant. Also, the performance criterion here is supposed to be the energy consumption, but it can as well be the operating coast or the carbon dioxide emission equivalent.
Further according to the present invention, it is preferable that there are provided a computer for computing optima, which determines optimal control targets to minimize or maximize a performance criterion by simulation, and a monitoring/control unit which receives optimal control targets from the computer for computing optima and performs monitoring and control to ensure that constituent units of the air conditioning plant operate without abnormality, wherein the processing period of the monitoring/control unit is shorter than that of the computer for computing optima, and the monitoring/control unit adjusts the control targets, in response to variations in the conditions of outside air, the temperature of cooling water, that of cold water and other factors, so that the operational limits of the units be not surpassed with reference to the optimal control targets determined by the computer for computing optima. More accurate control of the operation of the air conditioning plant is thereby made possible.
Further according to the present invention, it is preferable that parameters required for air conditioning plant simulation are identified on the basis of measurements by sensors, the air conditioning plant is simulated using the identified parameters, and the parameters to be identified and the resistance coefficients of piping are ducting. This makes possible even more accurate control of the operation of the air conditioning plant.